This is what I found out: an estimated 40 million American women struggle with diminished sex drives. Some health professionals believe that low libido and diminished sexual desire have become a new epidemic in our society. According to recent estimates, more than one-third of women in the United States have problems with their sex drives. And even that number might be low, because lots of people (I know some of their names) may be too embarrassed to answer personal interview questions honestly.

Orgasmic disorders (where women either have never experienced an orgasm, called primary anorgasmia, or seem to have lost their ability to experience one, called secondary anorgasmia) affect approximately 25 percent of the female population in the United States. Do you know what these women do as they are having sex? You got it. The old Meg Ryan act (from the infamous scene in “When Harry Meets Sally“), faking orgasm (for those of you who never saw the flick), which can lead to more-complicated problems over time.

“[It] is about finding the balance that is necessary for your life energy–your essence–to flow freely. Sometimes a blockage stems from a physical problem, like a hormonal imbalance in the body or a neurochemical imbalance in the brain (I’ve got them both). It might evolve from an emotional problem, such as depression (I’ve got that too) or low self-esteem (uh huh). A lack of intellectual stimulation (I read the paper) or spiritual fulfillment (I go to church) can dampen sex drive too.

Regardless of where a blockage originates, it can feed into other imbalances over time. Attention to all the elements that drive your life energy–physical, emotional, intellectual, and spiritual–is necessary for sexual desire to return.”

If you’re as imbalanced and messed up as I am, you interpreted those last two sentences like this: I’ll never ever orgasm.

Read on, though, because I looked long and hard for this paragraph:

“Rest assured, you don’t need to achieve absolute balance among the physical, emotional, intellectual, and spiritual components of your sexuality and your self in order to reclaim your desire (phew!). You can want sex again without resolving all the underlying issues that may be affecting your libido. For most women, the simple act of consciously and fastidiously attending to the need for balance is enough to bring about change.”

Hmmm. I don’t know about that. I guess I’ll try it. But knowing I’m a tad screwed up and wanting to do something about it have never made me horny before.

If I collected a nickel for every uninformed statement I’ve heard about mental illness, I could afford my own psych ward–an entire wing of a hospital.

Here are some of my favorites:

“People with mental illness are not the only ones who wake up with heavy things on their minds. The difference is that some of us acknowledge that our mood might not be good or productive and move on.”

“When you learn how to master your thoughts and control your emotions, you won’t need medication. Ditch the label of manic depression and train your mind to believe it’s possible to reprogram your thinking, because it is.”

“You obviously have issues you haven’t addressed. Once you get to the core of your anxiety and depression–once you get to your unconscious issues–you will be free.”

“You were born with everything you need to get better.”

They are all ways of saying one thing: that depressives are at fault for their disease.

Up until six months ago–when I started doing a massive amount of homework on the subject of depression and bipolar disorder–I, too, believed that I was to blame for my symptoms. I was embarrassed by my illness because I felt that I had, in some way, caused it.

All that changed when I began working with the right doctor, a sensitive and extremely intelligent woman from The Johns Hopkins Mood Disorders Center. Dr. Milena Hruby Smith, M.D., Ph.D. passed along to me research on the genetics and treatment of mood disorders.

Under her care, I learned that depression and bipolar disorder are more than imbalances of neurotransmitters (serotonin, norepinephrine, and dopamine), chemicals that bridge the synaptic clefts and pass messages to each other. These diseases are the result of organic changes in specific areas of the brain.

The limbic system (which includes the hippocampus, basal ganglia, and prefrontal cortex) helps to regulate a person’s sense of well-being, appetite, aggression, and sex drive. “Researchers have also identified the limbic system as the origin of imbalances in neurotransmitters,” writes Swartz. “In addition, brain imaging scans reveal a decreased metabolic rate in the caudate nuclei and frontal lobes of depressed people.”

In his book “Against Depression,” Dr. Peter D. Kramer, Professor of Psychiatry at Brown University, provides an overview of research studies that sketch out the effect of stress hormones in the prefrontal cortex of the brain. Based on a survey of cutting-edge medical research, he believes that it’s the devastation in the amygdala and hippocampus regions–the significant cell death and shrinkage, and the diminished capacity for nerve generation–that contributes to fragile moods.

Kramer is trying to use his research to change attitudes among psychiatrists and patients. “Psychiatrists have learned that depression is progressive, and there is widespread agreement that we need to interrupt it very promptly and decisively to prevent further deterioration,” he writes. From a public health perspective, he believes that “depression is the most devastating disease known to mankind.”

There are psychiatrists and neurologists out there like Helen S. Mayberg, M.D., Professor of Psychiatry and Neurology at Emory University School of Medicine in Atlanta, Georgia, who are using brain-mapping techniques to find out what’s happening inside the brain and how those functions are connected to our emotions.

“Thanks to refinements in brain-imaging technologies (higher resolution in PET scans and MRIs), scientists now know that there are regional patterns of brain activity–differences in specific circuits of the brain–that distinguish depressed people from non-depressed people,” she writes in an in-depth report in the October 2006 issue of “The Johns Hopkins Depression and Anxiety Bulletin.”

Mayberg sees this neurological perspective–focusing on specific brain circuits–as a new way of understanding depression, which coupled with a biochemical approach, can lead to more targeted treatments.

The research into the genetics of mood disorders continues to pinpoint the genes that may predispose individuals and families to depression and bipolar disorder. There has been remarkable success in locating and identifying genes associated with schizophrenia, and, more recently, with obsessive-compulsive disorder (the “transporter” gene SLC1A1). Researchers have confirmed a role for the gene G72/G30, located on chromosome 13q, in some families with bipolar disorder, and also evidence for genes on chromosome 18q.

In recent years researchers have been able to see what a genetic predisposition to depression looks like. For example, the National Institute of Mental Health conducted a compelling study involving a gene known as the “serotonin transporter gene.” Further studies will point to biochemical pathways of disease and could lead to development of new medications to alter those pathways.

But even as all the gene linkages and structural information is interesting and helpful, the far more convincing data for the biological basis of mental illness, according to my psychiatrist and other doctors, is the natural history of these diseases.

“It didn’t take us finding the cellular basis of HIV or cancer or tuberculosis to convince us that these were diseases,” Dr. Smith explained to me in a recent e-mail. “It was the stereotypical nature of their symptoms and natural history.”

She makes an important point: why should it take fancy science to convince people that mental illnesses are biological diseases? It didn’t with HIV, cancer, or TB.

Even if depressives aren’t fascinated by the biological basis of their condition (as I am), they should know this: Mental illness is a real (not imaginary) organic, brain disease. End of story.